Effects of temperature and material on sensing moisture content of pelleted biomass through dielectric properties

The production of pelleted biomass represents a significant emerging industry in the United States. Solid biomass can be formed from the waste products of different natural and manufactured products. In this study, the effects of temperature and pellet material type on the dielectric properties were investigated. The resulting information was used to develop temperature- and material-independent moisture prediction equations. Dielectric properties of peanut-hull, pine, and hardwood pellets were measured at microwave frequencies for temperatures between 10 °C and 50 °C and at moisture contents between 4.9% and 16.0%. Further work was performed in investigating the dielectric properties of pine, peanut-hull, and hardwood pellets to determine whether a “unified” calibration for moisture content might be developed. Results showed that a temperature-compensated calibration for moisture content could be developed for different pellet types with standard errors of calibration between 0.50% and 1.04%. In addition, a unified calibration for pine, peanut-hull and hardwood pellets at 20 °C was developed that provides moisture content for the materials with a standard error of calibration between 0.48% and 0.56%.